package zhouyang;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * 多个线程同时读一个资源类没有任何问题，所以为了满足并发量，读取共享资源应该可以同时进行。
 * 但是如果有一个线程想去写共享资源，就不应该再有其它线程
 */
class MyCache{
    private volatile Map<String,Object> map= new HashMap<>();
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
    public void  put(String key,Object value){
        readWriteLock.writeLock().lock();
        try {
        System.out.println(Thread.currentThread().getName()+"\t写入数据"+key);
   try {
       TimeUnit.MILLISECONDS.sleep(300);
   }catch (InterruptedException e){
       e.printStackTrace();
   }
    map.put(key,value);
        System.out.println(Thread.currentThread().getName()+"\t写入完成");

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            readWriteLock.writeLock().unlock();
        }

    }
    public void get(String key){
        readWriteLock.readLock().lock();
        try {
        System.out.println(Thread.currentThread().getName()+"\t读取数据"+key);
   try {
       TimeUnit.MILLISECONDS.sleep(300);
   }catch (InterruptedException e){
       e.printStackTrace();
   }
    Object result = map.get(key);
        System.out.println(Thread.currentThread().getName()+"\t读取完成"+result);

        }catch (Exception e){
            e.printStackTrace();
        }finally {
            readWriteLock.readLock().unlock();
        }
    }
}
public class ReadWriteLockDemo {
    public static void main(String[] args) {
        MyCache myCache= new MyCache();
        for (int i = 1; i <=5; i++) {
            final int tempInt = i;
            new Thread(()->{
            myCache.put(tempInt+"",tempInt+"");//lambda中只能有常量，所以这里用tempInt
            },String.valueOf(i)).start();
        }
        for (int i = 1; i <=5; i++) {
            final int tempInt = i;
            new Thread(()->{
                myCache.get(tempInt+"");
            },String.valueOf(i)).start();
        }
    }
}
